2 mm STL Adjustment

I have an existing STL file and a reference photo that clearly marks the exact area that needs attention. All I need is a precise 2 mm extension to that specific section—no other geometry changes, no texture work, just a clean lengthening so the model remains watertight and print-ready... (Budget: $10 - $30 AUD, Jobs: 3D Animation, 3D CAD, 3D Design, 3D File Scaling, Slicing & Print Preparation, 3D Modelling, 3D Print Design, 3D Rendering, 3ds Max)